Vaginal Bleeding

I'm just learning how to do head-to-toe checkups on my chins and I've just discovered that one of my girls is bleeding from her vagina. I noticed it a couple of days ago, but the blood was dry so I cleaned her off and figured I'd watch her for a few days. Today, the blood was fresh. She doesn't seem to be an different than usual, but she has been timid since I adopted her (mid-July). She is eating and playing fine and basically just being herself.

I have read that the only reasons they would bleed would be due to mating or giving birth (or miscarrying), or if there is some internal thing wrong. There has been no breeding going on here, and I don't believe there was before she came to live with me.

I'm planning on taking her into the vet this week, but I thought I would see if anyone here as ever dealt with this and what kind of questions I should be asking at the vet. Thanks in advance.